Propulsion method using catalytic decomposition of hydrazine

ABSTRACT

A method is provided for decomposing fuel comprising substantially hydrazine in which the hydrazine is brought in contact with a catalyst consisting essentially of solid porous Raney cobalt. The catalyst may be adheringly supported onto a substrate, such as a foraminous nickel substrate, which has particular use in a propulsion system wherein fuel injected into a propulsion chamber is caused to contact the catalyst, whereby to decompose said fuel and effectively produce propulsion.

v 1 5|:- Unite Sites atet [151 3,673,801

Goldberger July 4, 1972 541 PROPULSION METHOD USING [56] ReferencesCited DECOMPOSITION OF UNITED STATES PATENTS 3,021,667 2/1962 Griffin..60/2l9 X [721 Max Gddberge'i waPPmg 3,081,595 3/1963 Rose .....60/2l9x [73] Assignee: Pioneer Research, Inc, Man h t C 3,086,945 4/1963 Cohn..l49/36 X [22] Flled: Sept 1968 Primary ExaminerBenjamin R. Padgett[2]] App]. No.: 761,880 Attorney-Sandoe,Neill,Schottler& WikstromRelated US. Application Data 57] ABSTRACT [63] fgg g ggfl 'igg of Sept Amethod is provided for decomposing fuel comprising substantiallyhydrazine in which the hydrazine is brought in contact with a catalystconsisting essentially of solid porous Raney 52 l M 3.38. if ctffsifiicobamhecatalystmaybeadheflnglywppomdonmsub- [58] Field of Search252/459; strate, such as a foraminous nickel substrate, which has par-23/212 ticular use in a propulsion system wherein fuel injected into apropulsion chamber is caused to contact the catalyst, whereby todecompose said fuel and effectively produce propulsion.

3 Claims, 3 Drawing Figures PATENTEDJUL "4 m INVENTOR MAX GOLDBERG RATTORNEYS.

PROPULSION METHOD USING CATALYTIC DECOMPOSITION OF HYDRAZINE Thisapplication is a continuation-in-part of my U.S. Pat. application Ser.No. 583,057, filed Sept. 29, 1966 for Decomposition of Hydrazine and nowabandoned.

This invention particularly relates to the catalytic decomposition ofhydrazine and to an improved Raney cobalt catalyst useful in suchdecomposition.

In many applications, it is desirable to catalytically decomposehydrazine. For example, the catalytic decomposition of hydrazine isoften used in various propulsion systems using the byproducts ofdecomposition as the propellant jet. In addition, the decomposition ofhydrazine is often used in turbine systems in which decomposed hydrazineproduces the gas flow for propelling the turbine. Also, catalytichydrazine decomposition is used in fuel cells and is also useful in thespeedy formation of large gas volumes.

The art has provided various arrangements for catalytic decomposition ofhydrazine. However, the catalysts used have normally been formed of rareearths and the platinum black families. Such catalysts have manydisadvantages. In general, such catalysts are very expensive and arenormally nonconductive when in catalytic form. The nonconductivity orhigh resistance inhibits employment of such catalysts on the surface ofelectrodes. Also, since such catalysts are provided only throughrelatively sophisticated reduction processes from oxide compounds, ithas been found very difficult to form the catalyst in useful physicalforms. For example, it is not uncommon to use Raney nickel in the formof a powder or wet paste. Catalysts heretofore applied to supportingsubstrates had the disadvantage in that the bond was usually extremelyweak and during the reaction, the catalytic surface would often beseriously damaged and/or destroyed. This is particularly noticeable inpropulsion systems where vibration and high gas pressures and gas flowvelocities are encountered. In this connection, powdered Raney nickeland Raney cobalt have their limitations. In such systems, the catalystsare destroyed so rapidly that excessive amounts of catalysts must besupplied initially so that sufficient catalysts remain for the reactionthroughout the desired operating interval.

It is, therefore, an object of the present invention to provide animproved method for the catalytic decomposition of hydrazine using aRaney cobalt catalyst in the form of a coherent, solid, porous element.

Another object of the present invention is to provide an improved Raneycobalt catalyst in the form of a coherent, solid, porous element and amethod of making such catalyst.

A further object is to provide a propulsion system in which Raney cobaltin the form of a coherent, solid, porous element is an essentialcomponent of the system.

A still another object is to provide a method of propulsion bydecomposing a fuel comprising substantially hydrazine utilizing a Raneycobalt catalyst in the form of a coherent, solid, porous, structuralelement.

As an additional object, the present invention provides a method forproducing a coherent, solid, porous element of Raney cobalt for use indecomposing hydrazine.

These and other objects will more clearly appear when taken inconjunction with the following disclosure and the accompanying drawings,wherein:

FIG. 1 is a schematic representation in cross section of a propulsionmotor utilizing the invention;

FIG. 2 is a section taken along lines 2-2 of FIG. I; and

FIG. 3 is an enlarged fragment of a Raney cobalt catalyst in the form ofa coherent, solid, porous element.

Stating it broadly, the various embodiments of the invention reside in amethod for decomposing a fuel comprising substantially hydrazineutilizing a Raney cobalt catalyst in the form of a coherent, solid,porous element; in a method for providing propulsion by catalyticallydecomposing within a propulsion chamber a fuel comprised substantiallyof hydrazine, utilizing a coherent, solid porous element of Raneycobalt, in a method for immediately decomposing liquid hydrazine to forma large volume of gas; in a method for producing a coherent, solidporous element of Raney cobalt; and in the catalyst element itself.

The decomposition of hydrazine involves at least one, and usually both,of the reactions given in the Equations 1 and 2 set for th below:

Equation 1: BEN- H, N 4NI-I kcal.

Equation 2: N l-l N 2H kcal.

It has been found that a Raney cobalt catalyst according to the presentinvention exhibits surprising and unexpected characteristics as acatalyst in the decomposition of hydrazine.

As the starting time in propulsion systems is important, it has beenfound, surprisingly, that the Raney cobalt catalyst according to thepresent invention reduces the normally conventional starting time to afaction thereof.

In propulsion systems in which hydrazine is utilized as the main fuel oras one of the fuels, the decomposition rate is also important. Heat isreleased upon decomposition of hydrazine and this heat together with theincrease in volume resulting from the decomposition of hydrazine isutilized to obtain a propulsive stream of gases. The heat release isincreased in proportion to the increase in the speed of decomposition ofhydrazine. This is important whether hydrazine is used alone as thepropulsion fuel or whether other propulsion fuels or propulsive gasstreams are used. It has been found unexpectedly that the speed ofdecomposition of hydrazine is increased manifold if the catalyst of thepresent invention is used.

In accordance with one embodiment of the invention, a coherent, solid,porous Raney cobalt catalyst is formed. To form the catalytic surface,Raney cobalt surface powder consisting of 50 percent aluminum, 50percent cobalt, available commercially from W. R. Grace Corporation,Baltimore, Md., as No. 2713, 5050 aluminum-cobalt non-active powder, isused as the feed to an Avco plasma dynamic spray gun. An open meshmetallic screen or foraminous substrate is sprayed with the spray gunwhich at least partially melts the alloy powder during a sprayingprocess from a distance of five inches until the entire surface is builtup with a thin coating. The noale of the gun is then moved back toapproximately 10 inches and spraying continued until a surface sheet 0.5mm thick is built up. This process is repeated on the uncoated side ofthe screen. The coated screen is them immersed in a 5 percent sodiumhydroxide solution in water (50 grams of sodium hydroxide in 1 liter ofwater) at room temperature. Hydrogen evolves as the aluminum componentis leached from the alloy. When hydrogen evolution stops, thetemperature is raised in small steps and held until further hydrogenevolution stops. The final temperature employed is approximately C. Notall the aluminum need be leached out.

It is believed that the leaching of aluminum from the alu minum-cobaltalloy provides a catalytic Raney cobalt surface in which the cobalt hasa defect in'its lattice structure which assists in the catalyticdecomposition of hydrazine.

The catalyst provided by the invention for hydrazine decomposition canbe adapted by treatment to resist poisoning by sea water. This isimportant where the catalyst is employed in water-to-air rockets ormissiles.

An advantage of the Raney cobalt catalyst provided by the invention isthat it can be metallurgically prepared in very large sizes andquantities. The supporting substrates can be conductive metals and sincethe catalyst itself is conductive, a catalyst coated metal substrate canbe employed as electrodes in fuel cells using hydrazine as a fuel, withthe catalytic surface providing the anode electrode for the cells. Forother applications such as propulsion systems, the catalyst can beapplied to strong foraminous substrates such as ceramic honeycombsenabling the material to withstand high temperatures (over 2000 F)without deterioration and high stress without mechanical destruction. Asis apparent, the catalyst is economical since the basic material is bothcheap and available in large quantities. Further, the catalyst can beformed in self-supporting sheets.

The volume of the gases from the decomposition of the hydrazine isincreased more than a thousand fold upon decomposition. As will beappreciated, such an increase in volume will exert high loads andstresses on the catalyst. Additionally, the catalyst is generally heatedto a high temperature within a very short time. It has been found thatthe porous coherent catalyst of the present invention will withstandsuch loads and stresses including shock loads even when the startingtime is reduced and the decomposition rate is increased withoutsubstantially adversely affecting the catalytic element.

As illustrative of the efficacy of the catalyst in decomposinghydrazine, the following example is given:

EXAMPLE 1 A sheet of cm is prepared as detailed above, to provide acoherent, solid, porous catalytic Raney cobalt surface. On this sheet isdropped 80 cm N l-l 85 percent concentration (hydrazine hydrate) for 20minutes without interruption and catalytic decomposition continuedwithout change during the reaction time. This demonstrates that thehydrazine has been catalytically decomposed and is not reacting with themetallic structure. During the reaction some ammonia fumes are evolved,indicating that both reactions of Equations 1 and 2 are underway.

The catalyst is subject to drop tests, as indicated in Example 2. Forthis test, 100 mg of Raney cobalt catalyst is prepared. Hydrazine 85-90percent concentration is then applied to the 100 mg of Raney cobalt indrops. The time for initiation of reaction and the running time of thereaction for complete decomposition is given in Example 2.

Several observations can be made from the test provided in Example 2.The first observation is that the catalytic material improved in thespeed of reaction after the initial reaction. Thus, when the first dropwas applied, 30 seconds elapsed before reaction was initiated. When thesecond drop was applied, the time of the reaction decreased to 1 secondand, by the fourth run,'the reaction was spontaneous. Similarly, therunning time improved after the initial run. It will, of course, benoted when three drops were applied, the reaction time increaseddisproportionately, indicating that the small amount of catalyst hadbeen flooded and the reaction inhibited by the lack of mechanicalcontact between the entire mass of hydrazine and the catalytic surface.

For propulsion systems, the decomposition method employing the Raneycobalt catalyst offers certain additional advantages. For example,common fuels for propulsion systems utilize hydrazine and hydrogenperoxide reacted together in the propulsion chamber. Using the catalystprepared as explained above, provides a propulsion arrangement withadvantages over existing systems. The hydrazine and the hydrogenperoxide are contained in independent tanks and admitted to a propulsionchamber by spraying the fuels on the catalyst surface. In addition,however, the large surface area provided by the leaching of the aluminumfrom the Raney cobalt alloy decomposes the hydrogen peroxide. Thus, withsuch a propulsion system, the propelling force may be obtained fromeither of the two fuels or from the combination of the two fuels. Thespecific impulses obtainable are provided in Example 3.

(minimum) Similarly, a propulsion fuel consisting of a mixture ofhydrazine and ammonium nitrate, Nl-L, N0 may be used. This fuel has theadvantage that the two components can be mixed and applied to the Raneycobalt catalyst in the propulsion chamber. However, hydrazine can beused alone.

Discussing the drawings in detail, the propulsion motor comprises anouter cylinder 10 having located within it a tank 24 containing someinert gas, such as nitrogen, under pressure. The tank 24 has an exitpipe 28 connecting said tank to tank 12 also within the cylinder. Tank12 contains liquid hydrazine. Valve 26 is provided in the pipe 28 sothat the inert gas from tank 24 can be connected to or shut off from thetank 12. Tank 12 has an exit pipe 30 coupled to control valve 16 whichcontrols the flow of hydrazine to nozzle 34.

The lower part of cylinder10 contains a firing chamber 36 i whichterminates into a constricted portion 38. The cylinder thereafter isflared outwardly as shown at 40. A barrier 32 separates the firingchamber 36 from the storage part of cylinder 10. Pipe 30 and nozzle 34pass through an appropriate orifice in the barrier 32, nozzle 34entering the firing chamber 36.

Anchored to the walls of cylinder 10 within the firing chamber 36 is thecoherent, solid porous catalyst of the present invention. Catalyst 20 isa sheet material rolled into a spiral formation as illustrated in FIG.2. In the arrangement shown, the porous solid Raney cobalt, which issupported on a flattened expanded or foraminous nickel sheet, is rolledsufficiently tight so that the maximum amount of catalyst can be locatedwithin the walls of cylinder 10. The catalyst 20 is securely anchored tothe walls of cylinder 10 and to screen 22.

One embodiment of the catalyst is shown in FIG. 3 comprising solid,porous Raney cobalt 43 in adhering contact to an expanded nickel sheet44, the Raney cobalt being on either or both sides of the sheet.Preferably, the expanded nickel sheet is flattened.

The operation of the propulsion motor may be conveniently arranged asfollows. Valve 26 is opened to allow the nitrogen to exert pressure onthe surface of the hydrazine in tank 12. The level of hydrazine in tank12 is indicated at 42. Valve 16 is opened slightly to spray initially asmall amount of hydrazine onto the catalyst 22. The hydrazine willdecompose and the temperature of the catalyst and the temperature in thefiring chamber 36 will be increased substantially. After the appropriatetime, which might be a few seconds or a few microseconds, valve 16 willbe opened fully to allow a predetermined maximum amount of hydrazine tobe sprayed onto the catalyst. The time of the initial spraying dependson the construction of the propulsion motor. It depends, additionally,on the treatment given to the catalyst and the ambient surroundings. Thecatalyst of the present invention is such that the starting time can bereduced to a few micro-seconds for a hot catalytic bed.

Hydrazine can be used as the only fuel, as illustrated above. Whereadditional fuel, such as hydrogen peroxide or ammonia nitrate areemployed, these may be introduced through a pipe 18 into cylinder 10 andsprayed by noale 14 onto the catalyst.

The propellant employed in the test comprised 74 percent by Weight NI-L, 25 percent by weight HN and 1 percent by weight H O. The tankpressure was 500 psi which resulted in a propellant flow of 50 grams persecond through the nozzle 18. The engine was run for 240 seconds,developing a maximum chamber pressure (downstream pressure) of 300 psiand developing -17 lbs. thrust. The steady state run was extremelysmooth with roughness less than :t 0.4 percent. The engine was pulsed atrandom during the run with the off time less than 1 second. Ignitiondelay (hot) was 3 milliseconds, response time 23 milliseconds and tailoff time less than 170 milliseconds. The chamber temperature ranged fromabout 1,400 to 1,800 F. To check catalyst deterioration, the engine wasstopped and rested for one week. At the end of the week, the engine wasrun for 600 seconds on hydrazine hydrate, 75 percent by weight. Thesecond run exhibited the same smooth steady state characteristics.

While the catalyst shown in FIGS. 1 and 2 is in the form of a tightlyrolled sheet, other arrangements can be used, for example, by placingthe Raney cobalt catalyst in any other shape and form within the firingchamber 36 so long as the solid, porous catalyst is structurally sound.

The Raney cobalt catalyst of the invention is particularly advantageousover Raney nickel in decomposing hydrazine. Comparison tests were madebetween Raney cobalt and Raney nickel supported on an expanded orforaminous nickel sheet.

The tests enable the comparison of the time required to start thedecomposition reaction and the total running time of the reaction. It isdesirable that the total running time be short as the amount of energyreleased per unit time has a bearing on the amount of generated thrustin a propulsion system. In carrying out the tests (note the tablebelow), a drop of hydrazine is dropped upon the catalyst and allowed toreact completely (Run. No. 1). Following completion of the reaction, asecond drop is added (Run No. 2). Following completion of the reactionof the second run, a third drop is added (Run. No. 3), and so on. Theresults obtained are as follows:

As will be noted from the foregoing table, both the Raney nickel andcobalt catalysts improve in the speed of reaction after the applicationof the first drop until the fourth addition of two drops of hydrazine(Run No. 4), following which the reaction is spontaneous. In the fifthand sixth runs, three drops each of hydrazine were added.

However, it will be noted that marked differences in behavior of the twocatalysts show up in the reaction time.

Using cobalt reaction time as a reference, it is observed that thehydrazine decomposes at a much slower rate with Raney nickel than withRaney cobalt (note the last column of the table). This difference isparticularly marked when two or more drops are applied to the catalysts(Run Nos. 4, 5 and 6), the reaction times for Raney nickel being 300percent, 440 percent and 500 percent, respectively, longer than thoseobtained for Raney cobalt.

The solid porous Raney cobalt catalyst may be used as an electrode.Self-supporting solid porous Raney cobalt is preferred in thisarrangement. A self-supporting solid porous Raney cobalt can be obtainedby spraying the Raney cobaltalurninum alloy onto a substrate andthereafter leaching away the substrate or removing it mechanically.Still another method of obtaining self-supportmg solid porous Raneycobalt is to peel the sprayed Raney cobalt from the substrate. Thealuminum and the substrate may conveniently be leached away with analkaline solution such as sodium or potassium hydroxide. Some residualaluminum up to 5 percent will normally remain; however, for mostapplications, this is not objectionable. Further leaching will removeeven this residual aluminum or any remaining substrate, if so desired.

Freshly prepared Raney cobalt is highly pyrophoric and is difficult tostore. The pyrophoric characteristic can be inhibited or substantiallyreduced by forming a superficial oxide film on the Raney cobalt, forexample, by conveniently immersing the same in water. Small amounts ofhydrogen peroxide may be added to the water to accelerate the formationof the oxide film. The initial decomposition of hydrazine will removethis oxide film from the surface of the Raney cobalt.

As stated above, the improved catalyst is solid, porous Raney cobalt.The term coherent" means that the porous Raney cobalt particles adhereto each other and are not in the fonn of loose, discrete particles suchas in the form of powder or granules. Preferably, the Raney cobaltcatalyst is adheringly supported on both faces of the substrate.However, it may be sufficient for some applications to have the catalystadheringly supported on one face of the substrate only.

Although the present invention has been described in conjunction withpreferred embodirnents, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and the appended claims.

What is claimed is:

l. A method for providing propulsion by catalytically decomposing withina propulsion chamber a fuel comprising substantially hydrazine whichcomprises, injecting said hydrazine into said propulsion chamber andcausing it to contact a catalyst consisting essentially of adherent,solid, porous Raney cobalt adheringly supported on a substrate, wherebyto decompose said fuel and effectively produce propulsion.

2. The method of claim 1, wherein said hydrazine is catalyticallydecomposed by causing it to contact said Raney cobalt adheringlysupported on a foraminous metal substrate.

3. The method of claim 1, wherein said hydrazine is catalyti callydecomposed by causing it to contact said Raney cobalt adheringlysupported on a ceramic honeycomb substrate.

73 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,673, 801 Dated July 4, 1972 Inventor(s) EX Goldberger It is certifiedthat error appears in theabove-identified patent and that said LettersPatent are hereby corrected as shown below:

'- Column 2, line 18, "faction" should read -fraction. 7 line 34, delete"surface" second occurrence Column 5, lines 40 to 50, table should readas follows;

Time for Reaction Reaction v Start Reaction Time Time Run. N H RaneyRaney Raney Raney t No. Ni Co Ni Co Ni Co l 1 drop 40 sec. 30 sec. 15sec. 4 sec. 375% 2 1 drop 2 sec. 1 sec. 6 sec. 4 sec. 150% 3 1 drop 2sec. 1 sec. 4 sec. 2 sec. 200% 4 2 drops spontaneous 6 sec. 2 sec. 300%4 3 drops spontaneous 22 sec. 5 sec. 440% 6 3 drops spontaneous 20 sec.4 sec. 500% Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD M,FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3,673,801 Dated July 4, 1972" Inventor Max Goldberger It iscertified that error appears in theabove-identified patent and that saidLetters Patent are hereby corrected as shown below:

[ Column 2, line 18, "faction" should read -fraction-. 4 I line 34,delete "surface" second occurrence Column 5, lines 40 to 50, tableshould read as follows:

Time for Reaction Reaction v Start Reaction Time Time Run. N H RaneyRaney Raney Raney No. Ni Co Ni Co Ni C0 1 1 drop 40 sec. 30 sec. 15 sec.4 sec. 375% 2 1 drop 2 sec. 1 sec. 6 sec. 4 sec. 150% 3 1 drop 2 sec. 1sec. 4 sec. 2 sec. 200% 4 2 drops spontaneous 6 sec. 2 sec. 300% 4 3drops spontaneous 22 sec. 5 sec. 440% 6 3 drops spontaneous 20 sec. 4sec. 500% Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. The method of claim 1, wherein said hydrazine is catalyticallydecomposed by causing it to contact said Raney cobalt adheringlysupported on a foraminous metal substrate.
 3. The method of claim 1,wherein said hydrazine is catalytically decomposed by causing it tocontact said Raney cobalt adheringly supported on a ceramic honeycombsubstrate.